The present invention generally relates to ink jet printer methods and more particularly relates to an ink jet printer method of providing an image on a receiver, so that the image has reduced graininess.
An ink jet printer produces images on a receiver by ejecting ink droplets onto the receiver in an imagewise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the capability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.
However, a major obstacle to achieving photographic quality with ink jet printer technology continues to be granularity, the perception of which is referred to as xe2x80x9cgrain.xe2x80x9d This deficiency is caused by the need to write discrete drops of ink as approximations to a xe2x80x9ctruexe2x80x9d (e.g., silver halide) continuous-tone photograph, which contains no inherent xe2x80x9cstructurexe2x80x9d (i.e., granularity) in the recording paper. Because of its inherent particulate nature, ink jet technology injects more xe2x80x9cstructurexe2x80x9d into its reproduction of images. This structure introduces noise and visual patterns, which can be visible despite sophisticated noise suppression processing techniques. In its attempt to match the smooth, grain-less images of silver halide, ink jet technology typically employs well-known techniques, such as spatial dithering via screening or error diffusion, which remove noise from visually sensitive low spatial frequencies and place it at higher frequencies. These techniques can suppress image-content noise, but the fundamental drop size (and consequently the spot size on the receiver) remains quite visible and generally can not be hidden by algorithms. A prior art technique is to use ever smaller drop sizes to overcome this problem. However, this prior art technique invites other difficulties, such as greater print head fabrication challenges, higher likelihood of nozzle contamination and failure as nozzle size shrinks, reduced yield of acceptable print heads with all nozzles capable of firing, greater mechanical precision required in drop placement and paper advance, and higher overall print head fabrication costs. Moreover, when designing a photographic system there should be a balance between graininess and sharpness. This is also true in ink jet technology. Sharp-edged dots can provide excellent text and line rendition; however, graininess is now enhanced as well. Soft-edged dots can have their tails overlapped to achieve smoothing of uniform density areas, but text and fine detail reproduction are blurred by this technique. Ideally, a photographic ink jet system should have dots of both profiles.
U.S. Pat. No. 5,764,252 describes a method for altering density of ink drops before ejection to provide images having density levels of varying intensity. This does not, however, eliminate the previously mentioned dot structure, which causes image graininess.
U.S. Pat. No. 5, 617,123 discloses a method to vary number of drops per receiver spot, which in turn alters spot size to achieve more density levels, but this technique does not fundamentally change spot morphology.
Therefore, there is a need to provide an ink jet printer method of providing an image on a receiver, so that the image has reduced graininess.
An object of the present invention is to provide a method of providing an image on a receiver, so that the image has reduced graininess.
With this object in view, the present invention resides in a method of providing an image on a receiver, so that the image has reduced graininess, comprising the step of providing a print head having a first segment capable of applying a liquid spreading agent and a second segment capable of applying an image forming liquid to the receiver, the spreading agent being applied to the receiver before the image forming liquid is applied to the receiver, so that the image forming liquid overlays the spreading agent and so that the image forming liquid is dispersed by action of the spreading agent.
As will be described below, the present invention allows adjacent dots on the receiver to spread and flow together, thereby drastically reducing any dot-like structure or appearance thereof and promoting a grain-less or continuous tone appearance instead. The invention also maintains image sharpness as the dots spread and flow together.
A feature of the present invention is the provision of a print head having a first segment capable of applying ink spreading agent and a second segment capable of applying a liquid ink to the receiver, the spreading agent being applied to the receiver at a plurality of image-wise specified locator positions before the ink is applied to the receiver at the locator positions, so that the ink overlays the spreading agent and so that the ink is thereafter dispersed by action of the spreading agent.
An advantage of the present invention is that use thereof reduces graininess in a conventionally generated ink jet image, while maintaining sharpness present in the image.
Another advantage of the present invention is that use thereof reduces sensitivity of the ink jet printing process to produce visible banding as caused by irregular print head or receiver transport motions.
Still another advantage of the present invention is that use thereof reduces and can even eliminate streaking caused by clogged nozzles or misdirected ink jets.
Yet another advantage of the present invention is that use thereof reduces and can even eliminate need for interleaving or xe2x80x9cnozzle averagingxe2x80x9d when writing images thereby yielding faster printing.
Still another advantage of the present invention is that use thereof permits use of larger drop sizes (e.g., about 10-15 picolitres).
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there are shown and described illustrative embodiments of the invention.